Andrea Alarcon reportedly was with a mayoral aide the night her daughter, 11, was left unattended at City Hall. The Board of Public Works president is the subject of a child endangerment inquiry.

Andrea Alarcon, president of the L.A. Board of Public Works, has taken a… (Ricardo DeAratanha / Los…)

A member of Los Angeles Mayor Antonio Villaraigosa's staff told police that she and city commissioner Andrea Alarcon were at a downtown hotel on the night Alarcon's 11-year-old daughter was found unattended at City Hall, sources told The Times.

Lorraine Green, an assistant to a top Villaraigosa aide, was the first to make contact with police officers as they searched past midnight for Alarcon, who is president of the city's Board of Public Works, according to law enforcement sources familiar with the Nov. 16 incident. The sources requested anonymity because an investigation is continuing.

The Times reported last week that Alarcon, 33, was the subject of a child endangerment inquiry. She has since announced she is seeking professional treatment; she did not specify what type.

Green, 42, is not a subject of the investigation but may be a witness, the sources said. Green did not comment on the matter when reached Thursday. Villaraigosa spokesman Peter Sanders said only that the mayor was not with Alarcon that night "at any time after he left City Hall," where he was honored at a gala thrown by Project Restore, a group that renovates city landmarks.

Alarcon, the daughter of Councilman Richard Alarcon, has taken a leave of absence and has not been charged or arrested in the City Hall incident. Earlier this year in San Bernardino County, she was charged with misdemeanor counts of drunk driving and endangering a child. Her attorney said last week that he expects all but one of the charges to be dropped.

Alarcon, who was appointed by Villaraigosa to her $130,000-a-year post, could not be reached. She released a statement last week saying her daughter is her "top priority and nothing could be more important."

The Times reported last week that Andrea Alarcon's daughter was found about 11:45 p.m. at City Hall. But new details indicate the girl was discovered unattended about an hour earlier.

According to law enforcement sources, the girl told police she secretly followed Alarcon out of City Hall about 10:30 p.m., as her mother walked with a man and woman she did not recognize. When the girl caught up at 1st and Main streets, Alarcon told her to go back and wait at City Hall, according to the sources.

Officers who patrol city buildings saw the 11-year-old not long afterward. About 11:45 p.m., the girl was taken to a Los Angeles Police Department station, the sources said.

About 1:30 a.m., Green called a city cellphone that Alarcon had provided to her daughter that night, according to the sources. After answering, the girl handed the phone to police. Green told police that she and Andrea Alarcon had been at the Doubletree by Hilton hotel two blocks away, according to the sources.

Once on the phone with police, Alarcon had trouble understanding what the officer was telling her, the sources said. She arrived at the police station about 2 a.m. and was interviewed by an employee of the county Department of Children and Family Services.